Effect of organic fertilizers on apparent nitrogen utilization and yield of sweet pepper (Capsicum annuum L.) as influenced by fertilizer timing

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Soil nitrate content (g NO3- N/m2) Soil nitrate content (g NO3-N/m2) 40 35 30 25 20 15 10 5 0 A 0 7 14 21 28 35 42 49 56 Time Fababean 20/0 g N/m2 Fababean 10/10 g N/m2 Fababean/Maltaflor 10/10 g N/m2 Maltaflor 20/0 g N/m2 Horn 20/0 g N/m2 Control 35 30 25 20 15 10 5 0 B 0 7 14 21 28 35 42 49 56 63 Time Fababean 20/0 g N/m2 Maltaflor 0/20 g N/m2 Maltaflor 0/10 g N/m2 Maltaflor 20/0 g N/m2 Horn 20/0 g N/m2 Control Fig. 1. Nitrate content in soil (0-15 cm) fertilized with fababean, Maltaflor (Maltaflor ® spezial) and horn at different N rates (10 or 20 g N/m 2 ) and times <strong>of</strong> application (before or six weeks after planting) in the glasshouse in 2012 (A) and 2013 (B). Discussion Yield and N uptake <strong>of</strong> sweet peppers fertilized with be caused by the <strong>of</strong>ten marginal effect <strong>of</strong> green manure on yield <strong>of</strong> sweet peppers on fertile soils, but plant-based and industry-processed <strong>organic</strong> N its high effects on poor soils (Thönnissen et al., <strong>fertilizers</strong> were similar to those fertilized with horn, indicating that they can substitute for animal residue based <strong>organic</strong> <strong>fertilizers</strong>. Comparably, Abdul-Baki (1996) measured higher marketable yield and fruit weight <strong>of</strong> sweet peppers grown in cover-crop mulches compared to bare plots without mulch. However, Tourte et al. (2000) found no significant differences in the yield <strong>of</strong> marketable sweet peppers between the control and an application <strong>of</strong> wooly pod vetch, although their N rate (approx. 175 kg N/ha) was similar to ours. These somewhat contrary results may 2000a). The N supply <strong>of</strong> the soil may be also the reason for the higher differentiation <strong>of</strong> sweet peppers yield between fertilized and unfertilized plots in 2013 compared to 2012. This differentiation was more pronounced for the N uptake than for the sweet peppers yield. The very high N uptake <strong>of</strong> the control in 2012 was partly related to the high nitrate input with the irrigation water (up to 5.3 g N/m 2 ) and partly the result <strong>of</strong> the high net N mineralization. Therefore, the effect <strong>of</strong> fertilizer application on yield and N uptake was low, resulting in an apparent N utilization Ng’ang’a et al. Page 59
<strong>of</strong> 19-33 %. In 2013 apparent N utilization <strong>of</strong> the same treatments was much higher (30-57 %) due to a markedly lower yield <strong>of</strong> the control. On one hand, any surplus <strong>of</strong> mineral N in soil may be prone to losses by leaching or immobilization (Blankenau and Kuhlmann, 2000). On the other hand, a minimum content <strong>of</strong> mineral N in soil is needed to support a proper plant growth (Feller and Fink, 2002). Therefore, a fertilizer application strategy like splitting that reduces intermittently occurring N excess in soil may be favorable. However, in 2012 the splitting <strong>of</strong> the N rate resulted neither in higher yield nor in higher N uptake or apparent N utilization <strong>of</strong> sweet peppers. In view <strong>of</strong> the missing yield differences, the N supply <strong>of</strong> the sweet peppers in both treatments was obviously not significantly different during crucial stages <strong>of</strong> development. Therefore, from a split application <strong>of</strong> a readily available <strong>organic</strong> fertilizer like Maltaflor ® -spezial, a higher N efficiency might be expected. However, particularly if soil N release is low a single late fertilizer application even with a readily available <strong>organic</strong> fertilizer like Maltaflor ® -spezial runs the risk <strong>of</strong> yield deprivation. Similar results are presented by Båth (2001): a late application <strong>of</strong> green manure (clover) caused a delay in growth and N uptake <strong>of</strong> leek and high values <strong>of</strong> nitrate in soil at harvest. However, further experiments must substantiate the positive yield effect <strong>of</strong> a split fertilizer application <strong>of</strong> Maltaflor ® - spezial in contrast to those <strong>of</strong> fababean. Conclusions The tested <strong>fertilizers</strong> Maltaflor®-spezial and fababean will act as rapid N sources, ensuring a sufficient N supply for vegetable crops in <strong>organic</strong> horticulture comparable to those <strong>of</strong> established animal-based <strong>organic</strong> <strong>fertilizers</strong> like horn. Vegetable crops with a long-lasting growth period should be fertilized before planting. During the vegetation period a regular hoeing <strong>of</strong> the formerly fertilized plots will generally increase N mineralization and should therefore be part <strong>of</strong> an optimized fertilizer management strategy. Data suggest that a split application is more promising with a readily available <strong>organic</strong> fertilizer like Maltaflor®-spezial compared to fababean. References Abdul-Baki AA. 1996. Fresh-market pepper production in a low-input alternative system using cover-crop mulch. HortScience 31, 65-69. Båth B. 2001. Nitrogen mineralization and uptake in leek after incorporation <strong>of</strong> red clover strips at different times during the growing period. Biological Agriculture and Horticulture 18, 243-258. Blankenau K, Kuhlmann H. 2000. <strong>Effect</strong> <strong>of</strong> N supply on apparent recovery <strong>of</strong> fertiliser N as crop N and Nmin in soil during and after cultivation <strong>of</strong> winter cereals. Journal <strong>of</strong> Plant Nutrition and Soil Science 163, 91-100. FAO. 1998. World Reference Base for Soil Resources, FAO, Rome. Feller C, Fink M. 2002. NMIN target values for field vegetables. In: Booij, R., Neeteson, J. (ed.): Acta Horticulturae 571, Proceedings <strong>of</strong> the ISHS workshop: Towards an ecologically sound fertilisation in field vegetable production, International Society for Horticultural Science, 195-201. Gee GW, Bauder JW. 1986. Particle-size analysis. In: Klute, A. (ed.): Methods <strong>of</strong> soil analysis. Part 1. 2 nd ed. Agronomy Monograph. 9. ASA and SSSA, Madison, WI., pp. 383-411. Haworth F. 1961. The effect <strong>of</strong> <strong>organic</strong> and in<strong>organic</strong> nitrogen fertilizer on the yield <strong>of</strong> early potatoes, spring cabbage, leeks and summer cabbage. Journal <strong>of</strong> Horticultural Sciences 36, 202-215. H<strong>of</strong>fmann G. 1997. Die Untersuchung von Böden. In: VDLUFA-Methodenbuch, Band I, 4th ed., VDLUFA, Darmstadt. Iritani W M, Arnold C Y. 1960. Nitrogen release <strong>of</strong> vegetable crop residues during incubation as related to their chemical composition. Soil Science 89, 74-82. Koller M, Alföldi T, Siegrist M, Weibel F. 2004. A comparison <strong>of</strong> plant and animal based fertiliser for the production <strong>of</strong> <strong>organic</strong> vegetable transplants. In: Nicola, S., Nowak, J., Vavrina, C.S. (ed.): Acta Horticulturae. 631, XXVI International Horticultural Congress: Issues and advances in transplant production and stand establishment research, Ng’ang’a et al. Page 60
Page 1 and 2: RESEARCH PAPER OPEN ACCESS
Page 3 and 4: Table 2. N and C content and C/N ra
Page 5: Table 4 B: Cumulative N uptake <str

Effect of organic fertilizers on apparent nitrogen utilization and yield of sweet pepper (Capsicum annuum L.) as influenced by fertilizer timing

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